Hypodermic syringe

ABSTRACT

A syringe for the injection or taking of fluids having a needle mounting endpiece which is detachably coupled to barrel by mating features. A plunger and a coupled seal are guided by flanges sliding within guides and are further guided by protrusions so as to prevent rotation of the plunger and prevent unwanted contact between the flanges and the barrel. The plunger exhibits a bayonet-type fixture which upon rotation engages within the endpiece and allows retraction of the endpiece and coupled needle within barrel. Following engagement and retraction, the plunger may be prevented from movement by the engagement of protrusion on the barrel protrusions and abutment of radial protrusions against annular protrusions. Further embodiments and improvements are provided.

FIELD OF INVENTION

This invention relates to hypodermic syringes and similar devices suchas are utilised both for the injection of medicine into the body tissuesof, and the taking of fluid samples from, human and animal patients.Thus it may also be applied to additional equipment requiring a similarfunction. It is particularly concerned with reducing the risk of crossinfection through contact with or use of such syringes.

Disposable syringes are used throughout medicine and once used areusually discarded. However, the used needles are notoriously difficultto deal with; unsheathed they easily puncture bags and even whenreplaced within their originally sterile protective sheaths, they canfall out and present a hazard. This invention addresses the problems ofinadvertent stick injuries caused to health workers with contaminatedneedles after use, particularly when they are being re-sheathed prior todisposal and, after disposal, to ancillary personnel such as cleaners,the prevention of unauthorised re-use of syringes and the ease oftransportation of used devices.

BACKGROUND OF THE INVENTION

If problems such as those typified in the field of invention are to beovercome, needle and syringe combinations must be inexpensive toproduce, easy to operate and should conform to applicable standards inorder that they be widely utilised in the avoidance of such problems.

UK Patent Application GB 2 266 667 A describes such a combinationwherein a standard needle is coupled to a detachable end-piece which isaffixed to a syringe barrel. A flanged plunger which runs within guidesintegral to the barrel may, upon termination of use, be engaged intosaid endpiece by means of rotation in the manner of a bayonet typefixing. Having achieved engagement between said plunger and endpiece thecombination is withdrawn within the barrel of the syringe thus shieldingthe needle.

This system suffers from the fact that as the plunger may be repeatedlymoved to the extremes of axial travel allowing both the intake andexpulsion of fluids, an unavoidable volume (`dead-space`) of unexpelledfluid is inevitable since a further rotary motion is required in orderto engage to the endpiece and there is also no means provided ofevacuating fluid from within the central bore of the endpiece. It may benoted that such a dead-space is undesirable and, whilst this cannot becompletely eliminated, it is preferred that this unexpelled volume beminimised.

Furthermore this syringe requires that both the plunger and endpiece aresealed to the barrel in order to eliminate the leakage of fluid. This isachieved by the use of separate compressible sealing components whichare captured between the components to be sealed. Whilst the samecompressible component is utilised twice to serve this purpose, there isundesirable additional cost associated with this solution.

Additionally it may be noted that this syringe utilises an annulus ofperforations which are required to break or tear tangentially uponrotation of the plunger. This requires that the detachable portion ofthe endpiece and its support structure are formed integrally to eachother as one component.

The device is such that tearing force occurs in one direction and in oneplane. It has been observed that this single action does not provide theoptimum method of

breaking the perforations or initiating the withdrawal of theplunger/endpiece/needle. Furthermore it is identified that componentsincorporating such break-off features are sometimes difficult andexpensive to develop and may exhibit varying properties which may affecttheir performance.

Additionally, whilst the syringe provides a means of attaching theplunger/endpiece/needle combination to the barrel upon full retractionof the needle, there is little to inhibit the complete withdrawal ofthis combination from the barrel component, whereupon it would bere-exposed. In this eventuality the needle is once again undesirablyexposed and/or subject to interference.

GB 2 266 667 A represents the closest prior proposal currently known tothe applicant and the present invention was developed from it. Alsoknown to the applicant, however, and disclosed herein for the record,are the following published patent specifications:

    ______________________________________                                        GB 1454540           GB 2048077                                               US 4790822           US 5098402                                               EP 0327061           EP 0402908                                               WO 92/05820           WO 92/09320                                             ______________________________________                                    

Additionally, U.S. Pat. No. 5,242,419 discloses a syringe formed from abarrel having internal righthand threads at each end, a plunger whichsupports a piston near one end, and a tapered distal end provided with alefthand thread. The needle has a cap with an internal lefthand threadand a flange configured to engage the internal threads of the barrel.

U.S. Pat. No. 4,675,005 is directed towards a disposable syringe havinga locking device so that after use, a hub and cannula of the syringe canbe detached from the cylindrical body, withdrawn thereinto, and lockedthereto.

SUMMARY OF THE INVENTION

In view of the above considerations, it is therefore the aim of thepresent invention to provide a disposable hypodermic syringe which,through an ability to enable retraction of used needles within thebarrel and allow coupling of retracted needle and plunger to the barrel,reduces the aforementioned risks and, through the incorporation of anumber of detailed design features, overcomes the problems with existingdesigns of improved hypodermic syringes identified above.

The invention provides a hypodermic syringe, of a kind known generallyper se and comprising a barrel, a plunger and a needle-receivingendpiece, with guide means mounting the plunger slidably within saidbarrel so as to define a fluid chamber, and support means locating saidendpiece at least partially within said barrel to receive said needle inuse; the plunger--again in a manner previously proposed per se--beingnormally prevented by the guide means from rotating as it travelslinearly down the barrel to expel the fluid through the needle, butbeing freed from such preventative means when it reaches itsfully-depressed state; the arrangement being characterised by theprovision of appropriately profiled inter engaging surfaces formedrespectively on the exterior of said plunger and the interior of saidbarrel, whereby cooperation of said inter engaging surfaces duringrotation of said plunger when in its fully depressed state causes anautomatic and relatively slight axial retraction of said plunger suchthat the pressure in said fluid chamber is reduced, thereby tendingautomatically to draw any residual fluid away from the tip of saidneedle and back into said fluid chamber.

Preferably said appropriately profiled inter engaging surfaces compriseat least one angled face located at the needle-remote end of said barreland at least one radial protrusion located in that region of saidplunger which lies adjacent said angled face when the plunger reachesits fully depressed state.

The invention also encompasses a syringe as outlined above and wherein afinger protrudes from said plunger towards and ultimately--as theplunger approaches the endpiece in its fluid expelling travel--into acomplementary recess formed in said endpiece; characterised by thefeatures that the progressive entry of said finger into said recess actsso as to reduce the so-called dead space--the volume of unexpelledfluid--within said chamber and in that neither the finger nor the recessacts to inter engage said plunger with said endpiece at any point duringsuch entry.

Preferably said endpiece carries a sealing member which seals againstthe interior of said barrel so as to substantially prevent leakage offluid from said fluid chamber, characterised in that the sealing memberis formed integrally with said endpiece and in that the sealing memberexhibits in cross-section a flanged profile in which a gap is clearlyvisible between the barrel-contacting region of the seal and the rest ofthe endpiece of which the sealing member forms an integral part.

Preferably also said sealing member is of a double-lipped constructionin which two concentric and substantially annular projections form theseal with the interior surface of said barrel and said projectionswhilst being visibly separately defined are closely adjacent oneanother.

Where a screw-threaded inter engagement between the needle and theendpiece is provided to reduce the chances of inadvertent separation ofthe needle from the endpiece the thread is preferably formed on atapered surface and is thus a spiral thread.

Advantageously the crests of said thread when viewed in cross-sectionare substantially flat.

The roots of said thread when viewed in cross-section may be of anon-flat and preferably non-vee cross-section.

In a preferred arrangement wherein said endpiece further comprises anumber of recesses, each of which is interlockable with a correspondingone of a number of protrusions on the interior surface of said barrel,each of said recesses and protrusions is an annular recess and annularprotrusion respectively, the disposition and inter engagement of saidrecesses and protrusions is such that said endpiece is held within saidbarrel, before and during use, so as to substantially prevent unwantedmovement therebetween and said recesses and protrusions allow saidendpiece to be axially slidable within said barrel after use.

The invention includes specifically within its scope syringessubstantially as described herein with reference to and as illustratedin the accompanying drawings, since these constitute currently the bestways known to the applicant of putting the invention into practice.

BRIEF DESCRIPTION OF THE DRAWINGS

Four specific embodiments of the invention will now be described by wayof example with reference to the accompanying drawings in which:

FIG. 1 is a side view, partly in section, of a syringe assemblyembodying the present invention, orientated to allow use for withdrawaland injection of fluids;

FIG. 2 is a side view, partly in section, of the assembly shown in FIG.1 orientated to provide coupling between plunger and endpiece;

FIG. 3 is a side view, partly in section, of the assembly shown in FIGS.1 and 2 with plunger, coupled section of endpiece and hypodermic needlewithdrawn inside the barrel and coupling provided between plunger andbarrel so as to inhibit further motion;

FIG. 4 is a section through line AA of FIG. 1;

FIG. 5 is a section through line BB of FIG. 2;

FIG. 6 is a section through line CC of FIG. 1;

FIG. 7 is a section through line DD of FIG. 2;

FIG. 8 shows in perspective the upper end of the barrel shown in FIGS.1, 2 and 3;

FIG. 9 shows in perspective, partly in section, the upper end of thebarrel and the plunger shown in FIGS. 1, 2 and 3;

FIG. 10 is a side view, partly in section, of a syringe assemblyembodying the present invention as shown in FIG. 1 with an improveddesign of endpiece exhibiting an integrally moulded sealing means,orientated such as to allow use in a device for the withdrawal andinjection of fluids;

FIG. 11 is a side view, partly in section, of the assembly shown in FIG.10 with plunger, coupled endpiece and hypodermic needle withdrawn insidethe barrel and coupling provided between plunger and barrel so as toinhibit further motion;

FIG. 12 is a side view, partly in section, of a third syringe assemblyembodying the present invention as shown in FIG. 1 with an improveddesign of endpiece, orientated such as to allow use in a device for thewithdrawal and injection of fluids;

FIG. 13 is a side view, partly in section, of the assembly shown in FIG.12 with plunger, coupled endpiece and hypodermic needle withdrawn insidethe barrel and coupling provided between plunger and barrel so as toinhibit further motion;

FIG. 14 is a side view partly in section of a fourth syringe assemblyembodying the present invention as shown in FIG. 1 with an improveddesign of endpiece incorporating improved needle retention, orientatedsuch as to allow use in a device for the withdrawal and injection offluids;

FIG. 15 is a side view, partly in section, of the assembly shown in FIG.14 with plunger, coupled endpiece and hypodermic needle withdrawn insidethe barrel and coupling provided between plunger and barrel so as toinhibit motion;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 9, a plunger 11 slides within a barrel 10,flanges 16, 17, 18 and 19 sliding within guides 20, 21, 22 and 23respectively to prevent rotation of the plunger within the barrel 10. Ana elastomeric seal 12, located in annular groove 28, provides awatertight seal between the plunger 11 and the barrel 10. Flanges 16,17, 18, 19 extend along substantially the whole length of plunger 11.Guides 20. 21, 22, 23 extend downwardly from the "top end" of barrel 10(i.e the end furthest from the needle 15) to approximately 5 mm belowthe top end of barrel 10.

An endpiece 13 is coupled to the barrel 10 by means of projections 24and 25 fitting into corresponding annular grooves 26 and 27. Endpiece 13comprises an annular ring section 52 (see FIG. 7) and an "engagedsection" 51 which is adapted to engage a standard hypodermic needle 15.The two sections 51 and 52 are integrally formed, with engaged section51 being attached to annular ring section 52 by means of mouldingdetails 53-58. An elastomeric seal 14 located in annular groove 29provides a watertight seal between the endpiece 13 and the barrel 10. Ataper 30 provides coupling with the internal taper 31 of a standardhypodermic needle 15.

Under normal use, the plunger 11 slides within barrel 10 with bayonet 32moving within channel 33 at the bottom of travel and further travel isprevented by means of radial protrusions 34 and 35 locating withinannular grooves 36 and 37 respectively.

When plunger 11 is at the bottom of travel and bayonet 32 resides withinchannel 33, the dead-space of unexpelled fluid is minimised byprotruding circular finger 72 mounted on plunger 11 passing down bore 73thus displacing fluid. The fit between finger 72 and bore 73 is suchthat the volume of fluid displaced is maximised but coupling does notoccur.

Significantly, the relationship between circular finger 72 and bore 73is not used as a means of engagement between plunger 11 and endpiece 13(this being achieved by means of the bayonet 32 described below). Thecircular finger 72/bore 73 arrangement serves to reduce the volume ofunexpelled fluid i.e the significant problem of "dead-space" within thefluid chamber.

In addition, radial protrusions 67 and 68 in combination with guides 20,21, 22 and 23 on barrel 10 also provide guidance for the edges offlanges 17 and 19 and, by virtue of this, maintain clearance and inhibitcontact between flanges 16, 17, 18 and 19 and the inside face of barrel10.

Complete withdrawal of plunger 11 from within barrel 10 during use isinhibited by seal 12 being of such a design so as to be unable to passannular protrusions 39, 40, 41 and 42 without significant force toovercome the interference between seal 12 and the protrusions 39, 40, 41and 42.

After use plunger 11 slides within barrel 10 to the bottom of travelwith radial protrusions 34 and 35 locating within annual grooves 36 and37 respectively, bayonet 32 locates within channel 33 and circularfinger 72 locates within bore 73. At the bottom of travel, flanges 16-19have passed guides 20-23 and thus the plunger 11 is able to be rotated.Plunger 11 is rotated with annular protrusions 39, 40, 41 and 42 passingthrough recesses 43, 44, 45 and 46 respectively whilst radialprotrusions 34 and 35 moving within annular grooves 36 and 37 restrictthe degree of rotation of plunger 11 within barrel 10. During rotation,bayonet 32 engages endpiece 13 by moving under overhangs 47 and 48 andabutting against walls 49 and 50. Within this first sector of rotationof plunger 11 within barrel 10 and consequent rotation of radialprotrusions 34 and 35 within annular grooves 36 and 37, protrusions 34and 35 run along faces 82 and 83 of annular grooves 36 and 37. Theremaining sector of rotation of plunger 11 within barrel 10 causesengaged section 51 of endpiece 13 to break away from annular ringsection 52 of endpiece 13 through shearing of breakaway moulding details53, 54, 55, 56, 57 and 58. This rotational shearing is augmented andimproved upon by axial shearing induced by protrusions 34 and 35 beingforced to rise up angled faces 70 and 71, thus imparting an axial loadupon plunger 11 and engaged section 51 of endpiece 13.

Separation of endpiece 13 is thus improved by this additional axialforce. The additional axial force has the important effect of reducingthe pressure within the fluid chamber and/or needle as the plunger 11 isslightly withdrawn as a result of the above-mentioned axial force. Thisreduction in pressure tends to draw any residual (and potentiallycontaminated) fluid back into the syringe (i.e away from the end ofneedle 15) and thus significantly reduces the risk of fluid "spurting"or leaking from the needle 15 during the retraction process.

Plunger 11 is partially withdrawn out of barrel 10 with flanges 16, 17,18 and 19 sliding within guides 23, 20, 21 and 22 respectively, andengaged section 51 of end piece 13 and coupled hypodermic needle 15being simultaneously withdrawn inside barrel 10.

Towards the extreme of sliding travel of plunger 11 within barrel 10,radial protrusion 59 on flange 16 and radial protrusion 63 on flange 18pass and engage radial protrusions 67 and 68 of barrel 10, thusinhibiting further movement of plunger within barrel 10. Furthermoreradial protrusions 91 and 92 on plunger 11 abut against annularprotrusions 39, 40, 41 and 42 at the endpiece engaging end 38 of thebarrel 10 inhibiting further withdrawal of plunger/needle.

Referring to FIGS. 1, 10 and 11 a second embodiment of the invention isshown. An endpiece 84 provides an improvement upon endpiece 13 withinbarrel 10. Endpiece 84 improves upon endpiece 13 by exhibiting anintegral sealing member 74 which may carry sealing beads 75 and 85 inorder to augment its performance and thus eliminating the requirementfor elastomeric sealing device 14. Sealing member 74 may be caused toprovide a radial force against barrel 10 inhibiting the flow of fluidpast the endpiece 84. FIG. 11 illustrates such an embodiment of thissealing device in the retracted position with needle 15 positionedwithin barrel 10, central section 94 of endpiece 84 having moved bysliding within barrel 10.

Use of the integral sealing member 74 simplifies the construction of thesyringe, thus reducing production costs.

Referring to FIGS. 1, 12 and 13, a third embodiment of the invention isshown. An endpiece 86 provides an improvement upon endpiece 13 withinbarrel 10. Endpiece 86 improves upon endpiece 13 by exhibiting annularrecesses 77 and 78 which interlock with annular protrusions 79 and 80 onbarrel 10. By so doing endpiece 86 is coupled to and held by barrel 10in such a manner so as to prevent unwanted movement and inhibit removalduring normal use but, after use and following engagement of bayonet 32under overhangs 47 and 48, allow endpiece 86 to slide within barrel 10.By so doing endpiece 86 remains intact and is not required to exhibit,nor separate from, restraining means 53, 54, 55, 56, 57 and 58 aspresent in endpiece 13.

Referring to FIGS. 14 and 15 a fourth embodiment of the invention isshown. An endpiece 87, similar in design to endpiece 86, exhibits anadditional annular flange 88 with a number of raised protrusions 89 and90 on its inner face. These protrusions spiral in the manner of athreaded component in order to allow the engagement of two radialprotrusions frequently found on taper fitting needles. Once engaged inthe spiral the needle may be more securely coupled to the taper,endpiece and syringe by rotation of the needle causing the needleprotrusions to move along the axis of the spiral.

FIGS. 14 and 15 show that the crests of the thread (when viewed incross-section) are substantially flat, while the roots of the thread areof a non-flat, in this example curved, cross-sectional profile.

The present invention and embodiments thus provide improved methods ofcoupling of plunger to needle and withdrawal of needle within barrel,thus sheathing the needle and reducing the possibility of accidentalstabbing and, also in addition through coupling of withdrawn plunger andbarrel, a means of preventing re-use.

We claim:
 1. A hypodermic syringe comprising:a barrel; a plunger; aneedle; a frangible endpiece for receiving said needle; support meanslocating said endpiece at least partially within said barrel to receivesaid needle in use, guide means mounting the plunger slidably withinsaid barrel, so as to define a fluid chamber; said guide means havingpreventative means for normally preventing said guide means fromrotating as it travels linearly down the barrel so as to expel fluidthrough the needle but said plunger being freed from such preventativemeans when it reaches its fully depressed state; and means for causingautomatic and relatively slight axial retraction of said plunger suchthat the pressure in said fluid chamber is reduced, whereby tendingautomatically to draw any residual fluid away from the tip of saidneedle and back into said fluid chamber, said means includingappropriately profiled inter engaging surfaces formed respectively onthe exterior of said plunger and on the interior of said barrel, whichcooperate during rotation of said plunger when in its fully depressedstate to effect said slight axial retraction of said plunger and whichassist the frangible break-off of the endpiece.
 2. The syringe asclaimed in claim 1, wherein said endpiece carries a sealing member whichseals against the interior of said barrel so as to substantially preventleakage of fluid from said fluid chamber, characterized in that thesealing member is formed integrally with said endpiece and in that thesealing member exhibits in cross-section a flanged profile in which agap is clearly visible between the barrel-contacting region of the sealand the rest of the endpiece of which the sealing member forms anintegral part.
 3. The syringe as claimed in claim 2, wherein saidsealing member is of a double-lipped construction in which twoconcentric and substantially annular projections form the seal with theinterior surface of said barrel and in that said projections whilstbeing visibly separately defined are closely adjacent one another. 4.The syringe as claimed in claim 1, wherein a screw-threaded interengagement between the needle and the endpiece is provided to reduce thechances of inadvertent separation of the needle from the endpiececharacterized in that the thread is formed on a tapered surface and isthus a spiral thread.
 5. The syringe according to claim 4, wherein saidthread has crests which when viewed in cross-section are substantiallyflat.
 6. The syringe as claimed in claim 4, wherein said thread hasroots which when viewed in cross-section are of a non-flat and non-veecross-section.
 7. The syringe as claimed in claim 1, wherein saidappropriately profiled inter engaging surfaces comprise at least oneangled face located at the end of said barrel remote from said needleand at least one radial protrusion located in that region of saidplunger which lies adjacent said angled face when the plunger reachesits fully depressed state.
 8. The syringe as claimed in claim 1, whereina finger protrudes from said plunger towards and ultimately--as theplunger approaches the endpiece in its fluid expelling travel--into acomplementary recess formed in said endpiece; characterized in that theprogressive entry of said finger into said recess acts so as to reduce"dead space"--the volume of unexpelled fluid--within said chamber and inthat neither the finger nor the recess acts to inter-engage said plungerwith said endpiece at any point during such entry.
 9. The syringe asclaimed in claim 1, wherein said endpiece further comprises a number ofrecesses, each of which is interlockable with a corresponding one of anumber of protrusions on the interior surface of said barrel,characterized in that each of said recesses and protrusions is anannular recess and annular protrusion respectively, the disposition andinter engagement of said recesses and protrusions being such that saidendpiece is held within said barrel, before and during use, so as tosubstantially prevent unwanted movement therebetween, and in that saidrecesses and protrusions allow said endpiece to be axially slidablewithin said barrel after use.